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Parentheses, also called curved brackets (with a single one referred to as a parenthesis), have many functions in written language. The most frequent application is to set off supplementary material or side remarks. These are typically pieces of information that can be omitted without impacting the meaning or flow of the sentence. While commas can also serve this purpose, they can become confusing when used for other reasons, leading to clutter, as we see here.
Parentheses are also used when a writer is uncertain about the number (singular or plural) or gender (male or female) of a subject, and wants to cover all possibilities. In this case, the parentheses indicate that either option could apply.
In mathematics, parentheses serve several purposes, such as indicating coordinate pairs, isolating function arguments, and determining the order of operations. You may recall the mnemonic PEMDAS (or BODMAS or BEDMAS, if you're from the UK or Canada) from math class: when performing calculations, you resolve the expressions inside parentheses first, followed by exponents, then multiplication and division, and finally addition and subtraction (from left to right for the last four).
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Square brackets are mainly used to alter quoted material when the editor or writer is not the original author. These changes may include...
- Providing clarification - “He [the sheriff] shot them [the zombies] in the head.”
- Inserting missing information - “The zombies had entered the city from two neighboring counties [Butler and Beaver].”
- Filling in omitted words - “Where [are] the zombies at?”
- Making an editorial comment - “If you are bitten by a zombie, do not try to conceal it from your fellow survivors.” [emphasis mine]
- Using an ellipsis or the Latin term sic to show omitted text or confirm that the quotation matches the original exactly - “Oh muh gawd [sic], the zombies are coming through the window […]”
Square brackets are also useful for embedding secondary information within already existing subordinate text (this can be done by placing square brackets [like these] inside parentheses).
In mathematics, square brackets are utilized to represent floor and ceiling functions, commutators, matrices, intervals, and various other concepts I’m still trying to wrap my head around.
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Curly brackets, also known as squiggly brackets or braces, are rarely used in everyday writing but make appearances in poetry (to link triplet lines), music (to denote grace notes), mathematics (to indicate members of a set), and various programming languages (to enclose sets of instructions).
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Chevrons, or angle brackets, are mostly reserved for specialized contexts. In programming languages like HTML, they are used to mark tags and other expressions. In comic books, graphic novels, and video games, they are sometimes used around dialogue to show that a character is speaking a different language and that the text is a translation. On TV, they may surround sound effects (e.g., <explosion>) in closed captions to clarify the sound being made. In mathematics, they are employed to denote that one number is either less than or greater than another.
In more everyday settings, especially in online chats, angle brackets are used to create text symbols like hearts (<3) or to represent physical actions of the writer.
